#include <iostream>

  #include<cstdio>

  #include<cstring>

  #include<cstdlib>

  #include<stack>

  #include<queue>

  #include<iomanip>

  #include<cmath>

  #include<algorithm>

  using namespace std;

  int vis[],G[][],link[];

  int n;

  int find(int x)

  {

      int i;

      for(i=; i<=n; i++)

      {

          if(G[x][i]&&!vis[i])

          {

              vis[i]=;

              if(link[i]==||find(link[i]))

              {

                  link[i]=x;

                  return ;

              }

          }

      }

      return ;

  }

  int main()

  {

      int k,i,j,x,y,sum;

      memset(link,,sizeof(link));

      memset(G,,sizeof(G));

      cin>>n>>k;

      sum=;

      for(i=; i<k; i++)

      {

          cin>>x>>y;

          G[x][y]=;

      }

      for(i=; i<=n; i++)

      {

          memset(vis,,sizeof(vis));

          if(find(i))

          sum++;

      }

      cout<<sum<<endl;

      return ;

  }